In designing displays, such as instrumentation displays for automotive vehicles, it is desirable for appearance of a manufactured display to conform to display design. For example, it is frequently the case that all of the numerals and symbols of an automotive instrumentation display are designed to be the same color and brightness (i.e., luminance).
Regardless of the desire of designers, it is generally improbable that a manufacturer will manufacture a display with the exact color and luminance specified by the designer. However, if the display is manufactured with colors and luminance values close enough to the desired color and luminance value, i.e. within a specific tolerance, the display appears to the average observer to have the exact color and brightness desired by the designer.
Many studies have been published on the sensitivity of the human eye to color and brightness. Some of these studies provide data describing sensitivity of the eye to noticeable differences in color. In general, color appearance data can be represented on a three dimensional plot, with the first two dimensions describing the color value and the third dimension describing the luminance value. Typically, studies describe noticeable differences to a target color in the form of an ellipsoidal surface surrounding the target color on the three dimensional plot. See, e.g., Brown and MacAdam, "Visual Sensitivities to Combined Chromaticity and Luminance Differences," Journal of the Optical Society of America, vol. 39, no. Oct. 10, 1949.
In actual practice, it is not always clear whether a published work can be used to establish color tolerances for automotive displays because display symbols, such as those found in an instrument panel for a vehicle, differ in size, average luminance, and spatial distribution from the stimuli used in most of the published color discrimination studies. These factors affect the sensitivity of the eye to color and brightness differences. Studies supporting these findings include Poynter, "Color and Brightness Variability in Instrument Panel Appliques," 1987, (OS-33), Warren, Mich.: General Motors Research Laboratories; Poynter, "Variability in Brightness Matching of Colored Lights," Human Factors, 1988, 30(2), 143-151; Brown, "The Effect of Field Size and Chromatic Surroundings on Color Discrimination," Journal of the Optical Society of America, Vol. 42, No. 11, Nov., 1952; and Cornsweet, Visual Perception, 1970, Academic Press, Orlando, Fla., p. 82.
What is desired is a method of manufacture of displays enabling a manufacturer to ensure that manufactured displays appear to observers as designed.